Single-molecule magnets exhibit magnetic bistabililties at the molecular level, making them promising for molecule-based spintronics due to high magnetic densities. The incorporation of SMM behavior ...and electrical conductivity in one compound is rare because these two physical properties often do not operate in the same temperature range, which further hinders their use in practical applications. Here we present an organic–inorganic molecular hybrid, β″-(BEDO-TTF)3Co(pdms)2·(MeCN)(H2O)2 (BO3) (BEDO-TTF = bis(ethylenedioxy)tetrathiafulvalene and H2pdms = 1,2-bis(methanesulfonamido)benzene), which manifests both metallic conduction (electrical conductivity up to 1000 S cm–1 at 12 K under 2.0 gigapascal pressure) and SMM behavior in the temperature range 12–26 K for the first time.
Coordination complex (Cp*
2
Cr
III
)
+
{CpFe
II
(CO)
2
(Sn
II
PcCl
16
4−
)}
−
(
1
) has been obtained by the reduction of tin(
iv
) dichloride hexadecachlorophthalocyanine (PcCl
16
) by ...decamethylchromocene (Cp*
2
Cr) in the presence of {CpFe
I
(CO)
2
}
2
. The process is accompanied by oxidation of Cr
II
and Fe
I
centers and the formation of paramagnetic Cr
III
and diamagnetic Fe
II
species. Two-electron reduction of a macrocycle and the formation of diamagnetic PcCl
16
4−
as well as a transition of tin(
iv
) to tin(
ii
) occur. The PcCl
16
4−
tetraanions are formed in (cryptand(K
+
))
2
{Sn
IV
Cl
2
PcCl
16
4−
}
2−
·2C
6
H
4
Cl
2
(
2
) obtained by the reduction of Sn
IV
PcCl
16
by mild reductant - fullerene C
60
&z.rad;
−
radical anions. Complexes
1
and
2
precipitate as crystals. Sandwich-type assemblies are formed in
1
. Two (Cp*
2
Cr
III
)
+
cations are sandwiched between two {CpFe
II
(CO)
2
(Sn
II
PcCl
16
4−
)}
−
planes, whereas layers of the {Sn
IV
Cl
2
PcCl
16
4−
}
2−
macrocycles are formed in
2
. The formation of the PcCl
16
4−
tetraanions in both
1
and
2
is supported by the data of structural analysis, optical spectroscopy and magnetic measurements. Susceptibility measurements correspond to the contribution of one non-interacting Cr
III
spin (
S
= 3/2) per formula unit. Weak antiferromagnetic coupling is observed between the spins. Only Cr
III
atoms contribute to EPR spectra of
1
, whereas salt
2
is diamagnetic and EPR silent.
The crystalline paramagnetic complex based on ring-reduced tin(
ii
) hexadecachlorophthalocyanine has been obtained and characterized. Two paramagnetic (Cp*
2
Cr
III
)
+
cations are sandwiched between the diamagnetic {CpFe
II
(CO)
2
(Sn
II
PcCl
16
4−
)}
−
anions.
A new promising method for the preparation of crystalline 2D polymers based on tetra(4-pyridyl)porphyrin has been developed. Radical anion {H
2
T(4-Py)P&z.rad;
−
} species are used as the starting ...material. A new solid-state supramolecular array {H
2
T(4-Py)P}·{Tb
III
(TMHD)
3
}
2
·2.84C
6
H
14
(
1
) in which porphyrin units are bridged with Tb
III
ions to form a self-assembled 2D polymer has been obtained. The complex contains neutral porphyrin macrocycles, which is supported by optical and magnetic data. High-spin paramagnetic Tb
III
ions are weakly antiferromagnetically coupled in accordance with rather long distances between them.
A new crystalline hybrid organic-inorganic two-dimensional supramolecular polymer of the tetra(4-pyridyl)porphyrin and terbium(
iii
) complex, Tb
III
(TMHD)
3
, has been obtained and investigated.
Single-molecule magnets (SMMs) show superparamagnetic behaviour below blocking temperature at the molecular scale, so they exhibit large magnetic density compared to the conventional magnets. ...Combining SMMs and molecular conductors in one compound will bring about new physical phenomena, however, the synergetic effects between them still remain unexplored. Here we present a layered molecule-based compound, β′′-(BEDO-TTF)
4
Co(pdms)
2
·3H
2
O (
BO4
), (BEDO-TTF (BO) and H
2
pdms are bis(ethylenedioxy)tetrathiafulvalene and 1,2-bis(methanesulfonamido)benzene, respectively), which was synthesized by using an electrochemical approach and studied by using crystal X-ray diffraction. This compound simultaneously exhibited metallic conductivity and SMM behaviour up to 11 K for the first time. The highest electrical conductivity was 400-650 S cm
−1
at 6.5 K, which is the highest among those reported so far for conducting SMM materials. Furthermore, antiferromagnetic ordering occurred below 6.5 K, along with a decrease in conductivity, and the angle-independent negative magnetoresistance suggested an effective electron correlation between the conducting BO and Co(pdms)
2
SMM layers (d-π interactions). The strong magnetic anisotropy and two-dimensional conducting plane play key roles in the low-temperature antiferromagnetic semiconducting state.
BO4
is the first compound exhibiting antiferromagnetic ordering among SMMs mediated by π-electrons, demonstrating the synergetic effects between SMMs and molecular conductors.
A metallic single-molecule magnet was synthesised demonstrating simultaneous metallic conduction and excellent SMM properties at the same temperature range for the first time, with potential applications in molecule-based quantum spintronics.
Hexaazatrianthracene (HATA) and hexaazatriphenylenehexacarbonitrile {HAT(CN)6} are reduced by metallic iron in the presence of crystal violet (CV+)(Cl−). Anionic ligands are produced, which ...simultaneously coordinate three FeIICl2 to form (CV+)2{HATA ⋅ (FeIICl2)3}2− ⋅ 3 C6H4Cl2 (1) and (CV+)3{HAT(CN)6. (FeIICl2)3}3− ⋅ 0.5CVCl ⋅ 2.5 C6H4Cl2 (2). High‐spin (S=2) FeII atoms in both structures are arranged in equilateral triangles at a distance of 7 Å. An antiferromagnetic exchange is observed between FeII in {HATA ⋅ (FeIICl2)3}2− (1) with a Weiss temperature (Θ) of −80 K, the PHI estimated exchange interaction (J) is −4.7 cm−1. The {HAT(CN)6 ⋅ (FeIICl2)3}3− assembly is obtained in 2. The formation of HAT(CN)6.3− is supported by the appearance of an intense EPR signal with g=2.0037. The magnetic behavior of 2 is described by a strong antiferromagnetic coupling between the FeII and HAT(CN)6.3− spins with J1=−164 cm−1 (−2 J formalism) and by a weaker antiferromagnetic coupling between the FeII spins with J2=−15.4 cm−1. The stronger coupling results in the spins of the three FeIICl2 units to be aligned parallel to each other in the assembly. As a result, an increase of the χMT values is observed with the decrease of temperature from 9.82 at 300 K up to 15.06 emu ⋅ K/mol at 6 K, and the Weiss temperature is also positive being at +23 K. Thus, a change in the charge and spin state of the HAT‐type ligand to ⋅3− results in ferromagnetic alignment of the FeII spins, yielding a high‐spin (S=11/2) system. DFT calculations showed that, due to the high symmetry and nearly degenerated LUMO of both HATA and HAT(CN)6, their complexes with FeIICl2 have a variety of closely lying excited high‐spin states with multiplicity up to S=15/2.
Hexaazatrianthracene (HATA) and hexaazatriphenylene‐hexacarbonitrile {HAT(CN)6} ligands form coordination complexes with high‐spin (S=2) FeII atoms in dianion and radical‐trianion states. This provides weak antiferromagnetic exchange or ferromagnetic alignment of the FeII spins within the coordination assemblies.
Reduction of terbium(III) double-decker phthalocyanine, TbIIIPc2 (1), by sodium fluorenone ketyl in the presence of bis(triphenylphosphoranylidene)ammonium cations yields one-electron-reduced ...(PPN+){TbIII(Pc2–)2}−·2.5C6H4Cl2 (2) containing the dianionic Pc2– macrocycles, whereas a stronger NaCpCo(CO)2 reductant in the presence of an excess of cryptand yields two-electron-reduced {Cryptand(Na+)}2{(Pc2–)TbIII(Pc•3–)}2– (3) containing the Pc•3– radical trianionic macrocycle. Isolated pairs of the {TbIII(Pc2–)2}− anions are formed in 2, whereas compound 3 has unique 3D packing of the macrocycles with weak π-orbitals overlapping in all three directions. This is the first example of the two-electron-reduced lanthanide double-decker containing Pc•3– radical trianion studied in solid state. Compound 2 manifests single-ion magnet (SIM) behavior with a large effective spin-reversal energy barrier of U eff = 538 cm–1 in comparison with previously studied (Bu4N+){TbIII(Pc2–)2}− (U eff = 230 cm–1). Thus, changes in cation size and shape affect the molecular packing of {TbIII(Pc2–)2}− and increase the spin-reversal energy barrier. At the same time, two-electron-reduced species 3 containing TbIII and Pc•3– show no signs of SIM such as hysteresis loop at 1.9 K, and no peaks are observed on the temperature dependencies of in-phase (χ′) and out-of-phase (χ″) signals. In contrast to EPR silent 2, both compounds 1 and 3 manifest broad signals from paramagnetic TbIII ions. Narrower signals attributed to Pc•3– are of high intensity only in 3. In addition to the absorption bands of Pc in the UV and visible spectral range, compound 3 manifests the lowest energy absorption band in solid-state spectra even in the near IR range at 4700 cm–1 (2130 nm), whereas such bands are not observed in the spectrum of 2. These data show that the reduction of the Pc macrocycles in the lanthanide double-deckers leads to the appearance of new very low-energy new transitions associated with Pc•3– whose energy is the lowest among known reduced metal phthalocyanines.
Rational control of the molecular arrangement in solids has been the subject of intense research for many years. In particular, the structural control of bis(ethylenedithio)tetrathiafulvalene (ET) ...radical cations has attracted special interest because of the primary effect on the electronic properties of the salts. In this study, we obtained the first ET cation radical salts formed with nonuniform silver(I) complex polyanions, which involve multiple kinds of openings in the anionic layer, by an electrocrystallization method. θ-(ET)2Ag2(CN)N(CN)22 (1) with a θ-type ET packing motif contains double helical chains composed of AgN(CN)2, whereas α″-(ET)2Ag2(CN)(SCN)2 (2) with an α″-type ET packing motif contains zigzag ladders composed of AgSCN. Both silver(I)-based tube-like assemblies are connected to each other by a cyano group, affording nonuniform polyanionic structures. Although both salts show semiconducting behavior, there is a distinct difference in their spin geometry, with an S = 1/2 Heisenberg antiferromagnetic square lattice in 1, which is associated with charge disproportionation or dynamical charge fluctuation in the ET layers, and an S = 1/2 Heisenberg anisotropic triangular lattice in 2, which results in spin frustration in the ET layers. The ability of the nonuniform polymeric structures in the anionic layers to act as templates for various arrangements of ET radical cations is demonstrated.
Phenomena that occur in nonequilibrium states created by photoexcitation differ qualitatively from those that occur at thermal equilibrium, and various physical theories developed for thermal ...equilibrium states can hardly be applied to such phenomena. Recently it has been realized that understanding phenomena in nonequilibrium states in solids is important for photoenergy usage and ultrafast computing. Consequently, much effort has been devoted to revealing such phenomena by developing various ultrafast observation techniques and theories applicable to nonequilibrium states. This Account describes our recent studies of diverse photoinduced dynamics in a strongly correlated organic solid using various ultrafast techniques. Solids in which the electronic behavior is affected by Coulomb interactions between electrons are designated as strongly correlated materials and are known to exhibit unique physical properties even at thermal equilibrium. Among them, many organic charge-transfer (CT) complexes have low dimensionality and flexibility in addition to strong correlations; thus, their physical properties change sensitively in response to changes in pressure or electric field. Photoexcitation is also expected to drastically change their physical properties and would be useful for ultrafast photoswitching devices. However, in nonequilibrium states, the complicated dynamics due to these characteristics prevents us from understanding and using these materials for photonic devices. The CT complex (EDO-TTF)2PF6 (EDO-TTF = 4,5-ethylenedioxytetrathiafulvalene) exhibits unique photoinduced dynamics due to strong electron–electron and electron–phonon interactions. We have performed detailed studies of the dynamics of this complex using transient electronic spectroscopy at the 10 and 100 fs time scales. These studies include transient vibrational spectroscopy, which is sensitive to the charges and structures of constituent molecules, and transient electron diffraction, which provides direct information on the crystal structure. Photoexcitation of the charge-ordered low-temperature phase of (EDO-TTF)2PF6 creates a new photoinduced phase over 40 fs via the Franck–Condon state, in which electrons and vibrations are coherently and strongly coupled. This new photoinduced phase is assigned to an insulator-like state in which the charge order differs from that of the initial state. In the photoinduced phase, translations of component molecules proceed before the rearrangements of intramolecular conformations. Subsequently, the charge order and structure gradually approach those of the high-temperature phase over 100 ps. This unusual two-step photoinduced phase transition presumably originates from steric effects due to the bent EDO-TTF as well as strong electron–lattice interactions.
Crystalline {Cryptand2.2.2(Na+)}{HAT(CN)6.−}⋅0.5C6H4Cl2 (1), {Cryptand2.2.2(K+)}{HAT(CN)6.−} (2), (CV+){HAT(CN)6.−} (3), and (CV+){HAT(CN)6.−}⋅2C6H4Cl2 (4) salts (where CV+ is the crystal violet ...cation) containing hexaazatriphenylenehexacarbonitrile radical anions have been obtained. The solid‐state molecular structure as well as the optical and magnetic properties of HAT(CN)6.− are studied. The formation of HAT(CN)6.− in 1–4 leads to the appearance of new bands in the visible range, at 694 and 740 nm. The HAT(CN)6.− radical anions have spin state S=1/2 and are packed in one‐dimensional stacks containing the {HAT(CN)6.−}2 dimers alternated with weaker interacting pairs of HAT(CN)6.− in 1 and nearly isolated {HAT(CN)6.−}2 dimers in 2. The {HAT(CN)6.−}2 dimers are diamagnetic in 1 but they effectively mediate one‐dimensional antiferromagnetic coupling of spins within the stacks with moderate exchange interaction of J/kB = −80 K. The behaviour of salt 2 is described by a singlet–triplet model for the {HAT(CN)6.−}2 dimers with an energy gap of 434(±7) K. Magnetic behaviour of both salts agree well with the data of extended Hückel calculations. Salts 3 and 4 contain isolated stacks of alternated HAT(CN)6.− and CV+ ions, and in this case, nearly paramagnetic behaviour is observed with Weiss temperatures of −1 and −7 K, respectively. Narrow Lorentzian EPR signals with g = 2.0033–2.0039 were found for the HAT(CN)6.− radical anions in 1 and 4 but in solution g‐factor shifts to 1.9964. The electronic structure of HAT(CN)6.− is analysed based on X‐ray diffraction data for 2, showing a Jahn–Teller distortion of the radical anion that reduces the symmetry from D3h to Cs and splits the initially degenerated LUMOs.
Crystalline radical‐anion salts of hexaazatriphenylenehexacarbonitrile {HAT(CN)6} radical anions with {Cryptand2.2.2(M+)} and CV+ cations were obtained. The solid‐state molecular structure as well as the optical and magnetic properties of HAT(CN)6.− are studied for the first time. When the stacks are formed only by HAT(CN)6.− (S=1/2), a strong antiferromagnetic coupling of spins is manifested.
The reduction of copper(
ii
) octafluoro- {Cu
II
(F
8
Pc)} and hexadecafluorophthalocyanines {Cu
II
(F
16
Pc)} by NaCpCo(CO)
2
in the presence of cryptand2.2.2 yields new crystalline {cryptand(Na
+
...)}Cu
II
(F
8
Pc)&z.rad;
3−
−
·2C
6
H
4
Cl
2
(
1
) and {cryptand(Na
+
)}
2
Cu
II
(F
16
Pc)
4−
2−
·C
6
H
14
(
2
) salts. Together with two previously characterized salts of Cu
II
(F
x
Pc) (
x
= 8 and 16), this allows the study of the molecular structure and optical and magnetic properties of fluorinated copper phthalocyanines in different reduction states (−1 and −2). The blue shift of the Q-band increases together with the negative charge on the macrocycle, and new weak bands of the anions appear at 820-1013 nm. Alternation of the N
meso
-C bonds manifests itself in reduced macrocycles due to a partial disruption of macrocycle aromaticity. In the case of Cu
II
(F
8
Pc) this effect is nearly two times stronger for dianions than for monoanions. The alternation of the bonds is less pronounced for perfluorinated Cu
II
(F
16
Pc)
n
−
(
n
= 1, 2) anions most probably due to a partial delocalization of the negative charge on fluoro-substituents. The reduction also noticeably elongates the average C-F bonds in Cu
II
(F
8
Pc). The first reduction centered on the macrocycle leads to the formation of Cu
II
(F
8
Pc)&z.rad;
3−
−
in
1
with two
S
= 1/2 spins positioned on Cu
II
and the radical trianion (F
8
Pc)&z.rad;
3−
macrocycle. As a result, a broad EPR signal is observed with
g
= 2.1652 at RT attributable to both paramagnetic species having exchange interactions. The formation of dimerized stacks from Cu
II
(F
8
Pc)&z.rad;
3−
−
in
1
results in strong enough magnetic coupling of the (F
8
Pc)&z.rad;
3−
spins within the dimers (
J
/
k
B
= −21.8 cm
−1
), and weaker intramolecular coupling is observed between Cu
II
and (F
8
Pc)&z.rad;
3−
(
J
/
k
B
= −10.8 cm
−1
). Coupling between (F
8
Pc)&z.rad;
3−
spins from the neighboring dimers is nearly 1.5 times weaker (−14.6 cm
−1
). Under reduction conditions, a second electron also comes to the macrocycle forming diamagnetic F
16
Pc
4−
tetraanions. In this case
S
= 1/2 spin is preserved on Cu
II
. Magnetic coupling between these centers is weak due to the long distances between them in the Cu
II
(F
8
Pc)
4−
2−
chains of
2
. Salt
2
shows an EPR signal with a HF splitting characteristic of Cu
II
with
g
= 2.1806 (
A
= 20.11 mT), and
g
= 1.9597 at RT.
New salts based on reduced fluorinated copper(
ii
) phthalocyanines were obtained. The effect of reduction on the molecular structure and properties of the Cu
II
(F
x
Pc)
n
−
(
x
= 8 and 16) species in reduced states (
n
= 1 and 2) was studied.
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